Sumitomo Metal Mining Company, Ltd.

Kenji Ohmori

Toshiyuki Osako

Kayo Hashiguchi

Kouichi Yokosawa

Ryuichi Kuzuo

Takashi Ishikawa

Atsushi Kawamoto

Junya Tada

Hiroko Sekiya

Nobumitsu Oshimura

The objects of the present invention are to provide a highly weather-resistant iron-based magnet powder containing a rare-earth element, characterized by high coercive force in a practically important humid atmosphere, resin composition containing the same powder for bonded magnets, and bonded and compacted magnets containing the same powder. The present invention provides the above-described products by optimizing the functions and types of the phosphate coating film, uniformly formed over the surfaces of the iron-based magnet powder particles containing a rare-earth element.

Highly weather-resistant magnet powder and magnet produced by using the same

The objects of the present invention are to provide a method of producing highly weather-resistant iron-based magnet powder containing a rare-earth element, particularly characterized by high coercive force in a practically important humid atmosphere, highly weather-resistant magnet powder produced by the same method, resin composition containing the same powder for bonded magnets, and bonded magnet containing the same powder. The present invention provides a method of producing a magnet powder by crushing an iron-based magnet powder containing a rare-earth element in an organic solvent, wherein phosphoric acid is added to the solvent in which the powder is crushed.

Method of producing highly weather-resistant magnet powder, and product produced by the same method

Disclosed are magnetic discs having (A) a Cr-layer, as a lower layer, which has a composition comprising (1) substantially Cr or (2) 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Zr, Mo, Zn, W and Ta, and a balance of being substantially Cr, and (B) a magnetic recording medium layer, as an upper layer, which has a composition comprising (1) substantially Co, (2) 30% by weight or less of Ni and a balance of being substantially Co, (3) 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, and a balance of being substantially Co, (4) 30% by weight or less of Ni, 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, and a balance of being substantially Co, (5) 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, (6) 30% by weight or less of Ni, 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, (7) 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, or (8) 30% by weight or less of Ni, 10% by weight or less of one or more selected from Y, La, Ce, Pr, Nd, Sm, Gd, Tb and Dy, 10% by weight or less of one or more selected from Cu, Nb, Ti, V, Cr, Zr, Mo, Zn, W and Ta, and a balance of being substantially Co, both as formed on a non-magnetic substrate, except those where the lower layer has the composition (1) and the upper layer has the composition (1) or (2) as well as those where the lower layer has the composition (1) and the upper layer has the composition (5) or (6) containing only one or more of Cr, Ta and/or W. The magnetic discs have noticeably improved magnetic characteristics and/or corrosion-resistance.

Magnetic disc

A powder of a rare earth oxide, or a powder of a rare earth oxide and a rare earth metal is mixed with a powder containing iron, a powder containing boron and at least one material selected from among an alkali metal, an alkaline earth metal and a hydrogenated product thereof. The mixture is heated at a temperature of 900.degree. C. to 1200.degree. C. in a non-oxidizing atmosphere, subjected to wet treatment, and heated again at a temperature of 650.degree. C. to 1100.degree. C., whereby an alloy powder is obtained. Alternatively, the mixture is heated at a temperature of 900.degree. C. to 1200.degree. C., crushed into coarse particles, heated again at a temperature of 650.degree. C. to 1100.degree. C. and subjected to wet treatment. The powder is pulverized into a finer powder having an average particle diameter of 1 to 10 microns. The powder is used for making a magnet with a resin.

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Ichikawa, Japan

Kenji Ohmori